The major aims of our ongoing research have been: (a) to identify the early emergence and stability of children's hostile behaviors and their concomitant psychophysiological responses to stress, which may be risk factors for cardiovascular disease in adulthood; and (b) to specify their determinants. Our past studies examining the Type A behavior pattern, hostility, physiological responses and family interactive behaviors have primarily involved White, upper-middle class children and parents. We propose to extend our program of research to include the study of Black children and those from lower-middle to middle class families. This extension is important not only because these groups have been understudied, but also to examine developmental factors that may be important in accounting for the much higher incidence of hypertension and related disorders in Blacks and in lower and lower-middle class groups. However, we are adopting a somewhat different strategy of inquiry for the present proposal. Specifically, we will: (1) study the patterns of cardiovascular responses exhibited by Black and White children in order to better assess hemodynamic and autonomic nervous system mechanisms that underlie these responses; (b) examine how these hemodynamic patterns relate to cardiovascular risk factors such as body fat distribution, left ventricular geometry (via echocardiography), as well as insulin, glucose, and lipid levels; and (c) to explore a new conceptualization of hostility indices and cardiovascular risk factors. 160 Black and White children and adolescents of both genders will be recruited for participation, half being pre-pubescent (9-10 years old) and half being post-pubescent (15-16 years old). The first laboratory session will consist of a fasting venous blood draw, collection of anthropomorphic data, a psychophysiological stress protocol involving four tasks selected to elicit different autonomic nervous system responses, and completion of standardized questionnaires to assess hostility and social support. A second session will involve an echocardiographic assessment of left ventricular geometry and cardiac performance variables, the Type A Structured Interview, and an interview examining how subjects process information about hostile intentions and actions of others. The proposed project attempts to add significantly to the understanding of etiology of Black-White and social class differences in cardiovascular risk factors, and the role of hostility in this development.